1. Field of the Invention
The present invention relates to a method for forming a semiconductor light-emitting device, in particular, the method relates to a method to form a semiconductor laser diode with a mesa structure buried with a semi-insulating semiconductor layer doped with iron (Fe).
2. Related Prior Art
One type of a semiconductor laser diode (hereafter denoted as LD) has been well known where a mesa structure including an active layer formed on an InP substrate is buried by a burying layer. A Japanese Patent Application published as JP-H06-085390A has disclosed an LD with such an arrangement where the LD includes the mesa structure containing an n-type lower cladding layer, an active layer, a p-type upper cladding layer and a p-type contact layer, each sequentially grown on the n-type InP substrate, and a semi-insulating burying layer made of InP doped with iron (Fe) formed so as to bury the mesa structure.
Because irons in the burying layer behaves as an electron trap to show the semi-insulating characteristic, when it is in contact with a p-type layer, electrons trapped by iron atoms in the burying layer may recombine with holes injected from the p-type contact layer, which causes a current leaking path from the contact layer to the burying layer; accordingly, the efficiency to inject carriers within the active layer is reduced.
One solution to reduce such a leak current has been proposed, where an additional current blocking layer made of n-type InP is formed on the semi-insulating burying layer to electrically isolate the p-type contact layer from the semi-insulating burying layer. However, the path from the p-type cladding layer to the semi-insulating burying layer still exists and the current injection efficiency has a scope to be further enhanced.